import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 86136
 * Date: 2025-05-05
 * Time: 11:35
 */
public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");
        while(true) {
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.根据请求计算响应（服务器最关键的一点）
            String response = possess(request);
            //3.把响应返还给客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),
                    response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印日志
            System.out.printf("[%s:%d] req:%s resp:%s\n",requestPacket.getAddress(),requestPacket.getPort(),request,response);
        }
    }

    public String possess(String request) {
        return request;
    }
    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
